The present invention relates to apparatus and methods for anchoring marine seismic bottom geophones and associated cables at desired locations while shielding the geophones from ambient currents and providing good seismic coupling to the marine bottom surface.
As the search for oil and gas reserves has extended into more remote portions of the world, more hostile conditions have been encountered which interfere with conventional exploration techniques. The Cook Inlet area of Alaska is a good example of one of these areas. In portions of this area, the water is deep enough so that conventional marine exploration techniques can be used. However, in many areas, the water is too shallow for such conventional open water techniques. While shallow water techniques have been developed and used successfully in other portions of the world, the bottom surface conditions and high currents have interfered with their use in the Cook Inlet. The marine bottom in this area is generally hard, smooth rock surface with essentially nothing to anchor to. Daily tidal height changes can be in excess of 30 feet with resultant peak tidal currents of over 6 knots. A conventional shallow water exploration method requires the use of marine seismic cables positioned on the water bottom and in contact with the bottom surface for receiving seismic signals. However, the high current conditions tend to move the seismic detectors from their desired locations and also cause significant noise generation by movement of the geophones and the cables to which they are connected. The hard, smooth surface of the bottom makes ineffective any typical anchoring mechanism.